Conventionally, there is proposed a vehicular driving support system that includes a display unit with a horizontally-oriented display screen installed under a windshield; the display unit displays, on the display screen, a display object (specifically, a direction in which the display object exists) that is located in front of the vehicle (see, for example, Patent Literature 1).
The above-described system estimates, with reference to a viewpoint of a driver, a direction in which the display object actually exists, based on a positional relationship between the subject vehicle to which the head-up display is equipped and the display object. Then, the above-described system sets an on-screen position that overlaps with the estimated direction as a display position of the display object.
When the above-described technology is applied to a head-up display (hereinafter also simply referred to as a “HUD”) that displays information on a windshield of the vehicle, a display in which a predetermined guidance image (figure or the like indicative of the display object) is superimposed on the display position of the display object can be performed to the driver.
The guidance image is displayed in such a way as to be superimposed over the display object in the head-up display, and a forward view display (the display object) changes at a high speed when the vehicle travels at a high speed or travels a sharp turn. In this case, the guidance image moves corresponding to the change of the forward view in a follow-up manner. When the forward view display changes at a high speed, the display of the guidance image might disturb the driving or become annoying to the driver.
Regarding the above-described difficulty, Patent Literature 1 has disclosed a technical solution in which update of the display is halted or an update cycle is changed when the movement of a vehicle is intense (i.e., when the forward view of the vehicle changes at a high speed) to reduce the annoyance to the driver.
However, in a head-up display which displays the guidance image by superimposing the guidance image over the display object viewable by the driver, even when the above-described countermeasures are implemented, the annoyance felt by the driver cannot be removed completely.
In the above-described proposed technology, when the movement (or the operation state) of a vehicle becomes intense, the update of the guidance image is halted or the updating cycle is extended. In this case, the guidance images are displayed in a discrete manner. As a result, the guidance images may be significantly displaced from the actual position of the display object, and this may cause an annoyance of the driver.